The paper presents a study of the mosque of al-Karīmīyah, which is considered one of the oldest mosques in Aleppo city. Despite the importance of this mosque, no study has been allocated to it, which gives a special significance of this paper especially that the monuments of the city subject to severe ruin because of the current events in Syria in general. The paper examines the names of the mosque and its historical importance as demonstrated through its various functions. All renewal works at the building are considered and an architectural description is provided, which includes a new dating for some elements, in addition to an analytical study shows the origin of the mosque's elements and compares them to parallel examples. The paper included also a reading for all remaining inscriptions with facsimile figures made by the author and published for the first time. The study also elucidates the endowments that were allocated to the mosque during the Mamluk and the Ottoman periods, demonstrating the significance of its waqf. All plates have been taken by the author in 2010.